ICS1892 Datasheet, PDF (51/148 Pages) Integrated Circuit Systems – 10Base-T/100Base-TX Integrated PHYceiver

ICS1892
Chapter 7 Functional Blocks
7.5.6 10Base-T Operation: Smart Squelch
The Smart Squelch Function imposes more stringent requirements on the Link Monitor Function regarding
the definition of a valid link, thereby providing a level of insurance that spurious noise is not mistaken for a
valid link during cable installation.
The STA can control the execution of the Smart Squelch Function using bit 18.0 (the Smart Squelch Inhibit
bit in the 10Base-T Operations Register). When bit 18.0 is logic:
• Zero (the default), the ICS1892 enables the Smart Squelch Function. In this case, the Link Monitor must
confirm the presence of both data and a valid IDL at the end of the packet before declaring a link valid.
For example, in 10Base-T mode, the ICS1892 appends an IDL to the end of each packet during data
transmission. The receiving PHY sees this IDL and removes it from the data stream. Enabling this
function requires the receiving PHY to confirm the presence of this IDL before declaring a link valid.
• One, the ICS1892 disables or inhibits the Smart Squelch Function. In this case, the Link Monitor does
not have to confirm the presence of an IDL to declare a link valid (that is, the reception of any data is
sufficient).
7.5.7 10Base-T Operation: Carrier Detection
The ICS1892 10Base-T Carrier Detection Function establishes the state of the Carrier Sense signal (CRS),
based upon the state of the Boolean “transmitting” and “receiving” variables. These variables indicate
whether the ICS1892 is (1) transmitting data, (2) receiving data, or (3) in a collision state (that is, the
ICS1892 is both transmitting and receiving data on the twisted-pair medium, as defined in the ISO/IEC
8802-3 standard). When the ICS1892 is configured for:
• Half-duplex operations, the ICS1892 asserts the CRS signal when either transmitting or receiving data.
• Full-duplex operations (or when the ICS1892 is in the Repeater mode), the ICS1892 asserts the CRS
signal only when it is receiving data.
7.5.8 10Base-T Operation: Collision Detection
The ICS1892 10Base-T Collision Detection Function establishes the state of the Collision Detection signal
(COL) based upon both (1) the state of the Boolean ”receiving” variable and (2) the Transmit state
machine. When the ICS1892 is operating in:
• Half-duplex mode, the ICS1892 asserts the COL signal to indicate it is receiving data while transmission
of data is also in progress.
• Full-duplex mode, the ICS1892 always sets the Collision Detect signal to FALSE.
ICS1892, Rev. D, 2/26/01
© 2000-2001, Integrated Circuit Systems, Inc.
All rights reserved.
51
February 26, 2001